The present invention relates to a showerhead, an apparatus for processing a semiconductor substrate, and more particularly, to an apparatus having a showerhead and a method of distributing a gas using the same.
Semiconductor devices are provided for various data storage and processing applications having a high integration density and performance. To manufacture such high integration density and high performance semiconductor devices, it is generally important to use technology that will accurately form a thin film pattern on a semiconductor substrate.
The technology approaches for forming the thin film pattern on the semiconductor substrate may generally be divided into a physical vapor deposition (PVD) process and a chemical vapor deposition (CVD) process. In addition, it is known to form a thin film pattern by an atomic layer deposition (ALD) process that may more accurately form a thin layer.
The CVD and the ALD process may operate based on a chemical reaction between a source gas AX and a reaction gas BY. The chemical reaction process may be represented by the following chemical reaction equation:AX(g)+BY(g)→AB(s)+XY(g)
To facilitate the chemical reaction between the source gas and the reaction gas, the gases may be heated at a high temperature or may be exposed to a high voltage using a showerhead. The showerhead generally heats the source and reaction gases or exposes the gases to the high voltage as well as spraying the gases on the semiconductor substrate.
A conventional showerhead for converting a process gas into a plasma state is disclosed in U.S. Pat. No. 6,173,673 issued to Golovato, et al. The conventional showerhead typically has a cylindrical shape. The showerhead is generally disposed over a process chamber in which a semiconductor substrate is manufactured. The source and reaction gases may then be introduced into the process chamber through the showerhead.
FIG. 1 is a cross sectional view illustrating a conventional showerhead 100. Referring now to FIG. 1, the showerhead 100 has a cylindrical shape including an inner space. The showerhead 100 includes a head cover 110, and first and second plates 120 and 130 having holes shown as defining gas outlets 103. The first plate 120 is coupled to a lower face of the head cover 110. A diffusion space 102 is formed between the head cover 110 and the first plate 120 when they are coupled together. The second plate 130 is coupled to a lower face of the first plate 120.
A gas inlet 101 is formed through the head cover 110. The gas outlets 103 extend through the first and second plates 120 and 130. The gas inlet 101 is in fluid communication with the diffusion space 102. The diffusion space 102 is also in fluid communication with the gas outlets 103.
A source gas or a reacting gas is introduced into the showerhead 100 through the gas inlet 101. The gas flows downwardly from the gas inlet 101 and widely diffuses in the diffusion space 102. The gas may then be distributed on a semiconductor substrate (not shown) through the gas outlet 103. However, as the diffusion space 102 in the conventional showerhead 100 has a relatively small volume, gas distributions in the diffusion space 102 may vary significantly at different positions relative to the gas inlet 101 and with the number of gas inlets provided.
When a gas is introduced into the diffusion space 102 through a gas inlet 101 that is positioned at a central portion of the head cover 110, as shown in FIG. 1, the gas may be concentrated in a central portion of the diffusion space 102. The gas concentration in the central portion of the diffusion space 102 may cause the gas to be distributed preferentially on a central portion of the semiconductor substrate through the gas outlets 103 that are positioned at central portions of the first and second plates 120 and 130. Thus, a more extensive gas deposition reaction may be generated at the central portion of the semiconductor substrate as compared to an edge portion of the semiconductor substrate. As a result, a layer on the semiconductor substrate formed by the deposition reaction may have an uneven thickness that is gradually thinned from the central portion to the edge portion of the semiconductor substrate.
A layer having an uneven thickness may cause failure problems for a semiconductor device, such as deteriorating characteristics of the semiconductor device. Although various conventional technologies have been developed that are addressed to the above-mentioned problems, these technologies have failed to overcome the problems.
For example, in accordance with one known conventional technology, the gas inlet 101 is blocked and a gas pipe is built in the first plate 120. The gas is jetted out from the central portion of the first plate 120 to the head cover 110. Thus, more gas may be provided to the edge portion of the diffusion space 102 as compared to the central portion of the diffusion space 102. As a result, the gas distribution to the edge portion of the first and second plates 120 and 130 may be increased.
However, the gas distribution to the central portion of the first and second plates 120 and 130 may be decreased, whereas the gas distribution on the edge portion of the first and second plates 120 and 130 is increased. Therefore, the deposition reaction at the edge portion of the semiconductor substrate may exceed that at the central portion of the semiconductor substrate. As a result, a layer on the semiconductor substrate may have an uneven thickness that is gradually thickened from the central portion to the edge portion of the semiconductor substrate.
As described above, when the gas is not uniformly distributed on the semiconductor substrate from the conventional showerhead 100, the layer on the semiconductor substrate may have an uneven surface. When other layers are formed on the uneven surface of the layer in following processes, errors may be generated in the following processes, which may deteriorate performance characteristics of a semiconductor device.